On 12/31/2016 02:53 PM, Mike Stump wrote:
Also, I can't have the two generated .c files in the same translation unit (at
least in their current form) because gcc's too smart with optimizations. :)
You can inform the optimizer to stop doing that. volatile is but one way.
This informs it that it doesn't get to know what is really going on.
void foo(int, float) { }
void (* volatile foo_noinfo) (int, float) = foo;
foo_noinfo (1, 3.4);
mean call foo, and inform the optimizer it doesn't get to know what is going on.
foo (1, 3.4);
means call foo, and inform the optimizer that it knows everything. This is
more complete than noinline.
That is interesting. That means that I can cram all of this into a
single translation unit, so I can just generate a single header instead
(I had originally started this way). Very nice! :)
You might need to conditionalize the test to only run on those systems that can compile
and run the code, to do that you might need [istarget "triplet"], where triplet
is a system where you know it will work. I didn't check the code to see how portable it
was.
Other than being x86_64-specific and making heavy use of gcc extensions, the C
& C++ code is platform portable.
There need be no gcc or g++ on the build system, nor the host system. The only
thing you get is a C++ compiler on the build system. It is important that the
generator program not use anything that isn't in the language standard (no gcc
extensions here). In the under test code, you can use gcc extensions, but, if
you do that, the cost is that you can't then test binary compatibility with
Microsoft's compiler (if it doesn't support the extensions you use) a la the
struct-layout-1 methodology.
Well I'm learning all sorts of new things; I wasn't aware that the
testsuite was designed to run with other compilers! Does the Microsoft
compiler support building functions using the System V ABI? I had
presumed that they would just never do such a thing because it would
make it would easier to use FOSS on Windows, which is just
anti-monopolistic. Anyway, the test name "msabi" may be misleading;
it's goal is to test 64-bit Microsoft ABI functions that call System V
functions. So for the test to be meaningful, I would still need to be
able to at least declare a function as System V (even if I use an
assembler implementation) and for the compiler to properly call it.
I'm also testing gcc's force_align_arg_pointer attribute in this
program, and calling such ms_abi functions both normally and with an
intentionally mis-aligned stack using inline asm -- that test would
probably be useless on msvc. So I guess I will have to investigate to
find out if it's even possible to build this test on msvc. I suppose
one advantage of having part of the code generated is that some of the
tests can be skipped by just passing a parameter to the generator. I
made a bitmask for each test variation, so just passing -m 0x7b would
prevent generation of forced re-alignment tests.
Daniel
